Avoiding Initial Memory Heap Size Error

Question

I run a Java code with the following command:

$ java -Xms4G -Xmx4G myjavacode

My cpu\'s RAM capacity is 6GB.

However it always fail

Answer 1

You've exceeded the maximum heap size of your JVM. This is both JVM and OS dependent. In most 32-bit systems the maximum value will be 2Gb, regardless of the physical memory available.

Answer 2

By default Java will run in 32 bit mode. Be sure to give it the -d64 option to put it into 64 bit mode. Once in 64-bit mode, you shouldn't have any trouble allocating a 6GB JVM.

Answer 3

Actually, the maximum memory size on 32-bit systems can vary, being anything up to 4 GB, but 2 GB is a common value. It's often possible to re-link your kernel to increase this to 3 or 3.5 GB. The issue, of course, is that you just don't have the address space to map more memory. Have you tried a 64-bit machine?

Also, remember to set your ulimit higher before you do this.